Download Ch 23 Series and Parallel Circuits

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SERIES AND PARALLEL CIRCUITS
Vocabulary Review
For each description on the left, write the letter of the matching item.
________
1.
a circuit in which there is only one current path
a. ammeter
________
2.
a short piece of metal that melts if a current that is too
large passes through it
b. circuit breaker
________
3.
the occurrence when a circuit forms that has a very low
resistance
________
4.
a circuit in which there are several different paths for a
current
________
________
________
5.
6.
7.
c.
combination
series-parallel
circuit
d. equivalent
resistance
e. fuse
an automatic switch that opens a circuit when the
current reaches some set value, stopping electric
charge flow
f.
ground-fault
interrupter
g.
parallel circuit
a circuit that has some branches in parallel and some in
series
h. series circuit
i.
short circuit
the value of a single resistor that could replace all
resistors in a circuit without changing the current
j.
voltage divider
________
8.
a device used to measure the current in part of a circuit
________
9.
a device used to measure the potential difference
between two points
________
10. a device that detects small differences in current caused
by an extra current path and opens the circuit
________
11. a series circuit used to produce a voltage source from a
higher-voltage battery
k. voltmeter
SECTION 1 Simple Circuits
In your textbook, read about currents in series circuits.
Circle the letter of the choice that best completes the statement or answers the question.
1. The current is ____ a series circuit.
a. higher at the beginning of
c. lower at the beginning of
b. the same everywhere in
d. variable in
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2. In an electric circuit, the potential difference provided by the generator or other energy source,
Vsource, is equal to the ____ of drops in electric potential across the resistors.
a. difference
c. sum
b. product
d. average
3. Which of the following equations is not correct?
a. I  Vsource/(R1  R2)
c. I  Vsource/(R1  R2 R3)
b. I  Vsource/(R)
d. I  R3 (Vsource)/(R1  R2)
4. Which of the following equations computes the equivalent resistance for a series circuit with
four resistors?
a. R R1  R2  R3  R4
c. 1/R 1/R1  1/R2  1/R3  1/R4
b. R R1  R2  R3  R4
d. R R1  R2 R3  R4
5. In a series circuit, the equivalent resistance is ____ any single resistance.
a. larger than
c. equal to
b. determined by
d. smaller than
6. If the potential difference across the battery does not change, adding more devices in the
series ____ the current.
a. sometimes decreases
c. sometimes increases
b. always decreases
d. always increases
7. To find the current in a series circuit, first calculate the ____ .
a. potential difference
c. power
b. equivalent resistance
d. equivalent voltage
In your textbook, read about drops in electric potential in series circuits.
Answer the following questions. Use complete sentences.
8. Why must the net change in potential be zero as electric charge moves through a circuit?
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9. How do you find the potential difference across an individual resistor?
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10. What type of circuit is used as a voltage divider?
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11. What is the purpose of a voltage divider?
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12. What determines the resistance of a photoresistor?
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13. Name a device that employs the special qualities of a photoresistor. How does this device work?
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In your textbook, read about parallel circuits.
Refer to the circuit diagram below to answer questions 14–18. Circle the letter of the choice that best answers each
question.
14. What type of circuit does the diagram represent?
a. a series circuit
c. a combination series-parallel circuit
b. a parallel circuit
d. a tandem circuit
15. How many current paths are in this circuit?
a. one
c. four
b. three
d. five
16. How would you calculate the total current of this circuit?
a. Find the average of the currents through each path.
b. Subtract the currents through each path.
c. Add the currents through each path.
d. It is not possible to calculate total current for this circuit.
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17. If the 10- resistor were removed from the circuit, which would not be true?
a. The current through the 20- resistor would be unchanged.
b. The sum of the current in the branches of the circuit would change.
c. The total current through the generator would change.
d. The current through the 50- resistor would change.
18. Which of the following is true for this circuit?
a. The equivalent resistance of this circuit is smaller than 10 .
b. R  R1  R2  R3
c. R  1/R1  1/R2  1/R3
d. R  R1  R2  R3
SECTION 2 Applications of Circuits
In your textbook, read about safety devices.
For each statement below, write true or rewrite the italicized part to make the statement true.
1. _________________________
When appliances are connected in parallel, each additional
appliance placed in operation reduces the equivalent resistance
in the circuit and causes more charge to flow through the wires.
2. _________________________
A short, thin piece of metal in a fuse melts to break an
overloaded circuit.
3. _________________________
When a circuit breaker opens, it allows charge to flow in the circuit.
4. _________________________
Ground-fault interrupters can be used to detect small
differences in current caused by an extra current path.
5. _________________________
Electric circuits at home are primarily series circuits.
6. _________________________
Low resistance causes the current to be very small and may
result in a short circuit.
In your textbook, read about combined series-parallel circuits.
Answer the following question. Use complete sentences.
7. Describe the strategy you would use to calculate resistance in a combined series-parallel circuit.
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Circle the letter of the choice that best answers the following question.
8. Which diagram represents a combined series-parallel circuit in which a 30- resistor and a 75-
resistor are connected in parallel to a 125-V source through a 2- resistor in series?
a.
c.
b.
d.
In your textbook, read about ammeters and voltmeters.
Refer to the circuit diagram below to answer questions 9a–c.
9. Redraw the circuit diagram according to the following directions.
a. Insert a voltmeter that would measure the potential difference across the 10- resistor.
b. Insert an ammeter in the circuit that would measure the current of the entire circuit.
c. Insert an ammeter in the circuit that would measure the current through the 60- resistor.
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Write the term that correctly completes the statement.
10. _________________________
A(n) ____ measures the potential difference across a resistor.
11. _________________________
A(n) ____ measures current.
12. _________________________
The resistance of a voltmeter should be as ____ as possible so
that it will change the current as little as possible.
13. _________________________
The resistance of an ammeter should be as ____ as possible so
that it will change the current as little as possible.
14. _________________________
An ammeter is placed in ____ with the resistor if you want to
measure the current through the resistor.
15. _________________________
A voltmeter should be connected in ____ with a resistor to
measure the potential difference across that resistor.
16. _________________________
A(n) ____ always has low resistance and is connected in series.
17. _________________________
A voltmeter always has ____ resistance and is connected in ____
with the part of the circuit being measured.
18. _________________________
The result of connecting a(n) ____ across a resistor is to lower
the potential difference across it.
19. _________________________
The higher the ____ of a voltmeter, the smaller the voltage
change.
20. _________________________
If you want to measure the current in a branch or part of a
circuit, use a(n) ____ .
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Study Guide
Teacher Support
SERIES AND PARALLEL CIRCUITS
11. A voltage divider produces a voltage
source of desired magnitude from a
higher-voltage battery.
All numerical answers have been rounded to
the correct number of significant figures.
12. The resistance of a photoresistor depends
on the amount of light that strikes it. A
photoresistor is made of material that
naturally has a higher resistance in the
dark.
Vocabulary Review
1. h
2. e
3. i
13. A circuit that includes a photoresistor is
used in a light meter. The electronic
circuit detects the potential difference
and converts it to a measurement of
illuminance.
4. g
5. b
6. c
14. b
7. d
15. b
8. a
16. c
9. k
17. d
10. f
18. a
11. j
SECTION 2 Applications of
SECTION 1 Simple Circuits
Circuits
1. b
1. true
2. c
2. true
3. d
3. closes
4. a
4. true
5. a
5. parallel
6. b
6. large
7. b
7. First draw a schematic of the circuit. Then
reduce the problem to a set of series
circuits and a set of parallel circuits.
Combine the resistances of the parallel
circuits into one circuit, and calculate the
single equivalent resistance that can
replace them. That leaves only a series
circuit. Add the resistors in series to
calculate the equivalent resistance.
8. The circuit’s electrical energy source raises
the potential by an amount equal to the drop
in electric potential produced when the
current passes through the resistors. If the
net electric potential difference did not equal
zero, the circuit would violate the law of
conservation of energy.
9. Multiply the current in the circuit by the
resistance of the individual resistor.
8. a
10. A series circuit is used as a voltage divider.
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Study Guide
9.
Teacher Support
A
B
C
10. voltmeter
11. ammeter
12. high
13. low
14. series
15. parallel
16. ammeter
17. high, parallel
18. voltmeter
19. resistance
20. ammeter
Chapter 23  Series and Parallel Circuits
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